Lutin have a dangerous secret, and Kuro has stumbled headlong into it.

Book 4 Chapter 3 - Summer School

Living in secret and stealing to eat is a hard life, but it's all Kuro has ever known. Fear and necessity forged him into the finest young thief in the wizard kingdoms. Nobody can hide forever, though, and a run of poor luck lands Kuro in a place where his quick hands and quiet feet count for nothing: Avalon Academy, school of magic.